In the bottom of a crockpot, layer half of the frozen pierogi.

Add half of the sliced kielbasa and half of the diced onion on top of the pierogi.

Sprinkle half of the shredded cheddar cheese over the kielbasa and onion.

In a separate bowl, mix together the cream of mushroom soup, sour cream, garlic powder, onion powder, salt, and pepper until well combined.

Pour half of the soup mixture over the cheese layer in the crockpot.

Repeat the layering process with the remaining pierogi, kielbasa, onion, cheese, and soup mixture.

Cover the crockpot and cook on low for 6-8 hours or on high for 3-4 hours, until the pierogi are tender and the casserole is heated through.

Before serving, garnish with fresh chopped parsley.